# Evidence: buffer capacity

Parent: — · class: solution behaviour · names merged here: buffer capacity

4 papers measured or used it, 0 only mentioned it (of 207 kept papers). Papers in year order; each section heading ends with the paper's category / subcategory. Generated by tools/build_evidence.py from registry/concepts.csv and the cards; do not edit.

## 2022 Qi — Improved dissolution of an enteric polymer and its amorphous solid dispersions by polymer salt formation · Dissolution / A. Release mechanism and LoC

[2022-qi-enteric-polymer-salt-hp50-miconazole-asd-dissolution](../../../cards/2022-qi-enteric-polymer-salt-hp50-miconazole-asd-dissolution/paper.html) · Dissolution / A. Release mechanism and LoC · measured · as: buffer capacity

| id | kind | content | locator |
|---|---|---|---|
| R12 | record, derived (P10) | normalized dissolution rate (mg·min⁻¹·cm⁻²) at two buffer capacities, mean with SD bar, n = 3 — HP-50-Na and HP-50 compacts in 50 mM (M16) and 5 mM (M17) phosphate — sub-table below. Text: HP-50-Na rate the same in both media; HP-50 6-fold lower in 5 mM than in 50 mM phosphate | Fig. 8, p.6; text p.6, p.8 |
| M16 | material | phosphate buffer 50 mM, pH 6.8 6.96 g sodium phosphate dibasic anhydrous + 7.04 g sodium phosphate monobasic monohydrate in 2 L deionized water; labelled "75 mM Na" in Fig. 2 | p.2, p.3, p.4 |
| M17 | material | phosphate buffer 5 mM composition and pH not printed | p.6 |
| C4 | claim, conclusion, authors: asserted ("the same"; "not impacted") | A polymer salt (HP-50-Na) keeps a rapid dissolution rate irrespective of buffer capacity, whereas HP-50 dissolution falls greatly (6-fold from 29 to 3 mM·ΔpH⁻¹) as buffer capacity approaches gastrointestinal values [rests on: R12] | p.1, p.6, p.8 |
| C14 | claim, conclusion, authors: "it is apparent"; "clearly no correlation"; "appear to trend" | HP-50 dissolution rate depends strongly on the buffer species, with no correlation to cation size; it appears to trend with buffer pKa and buffer capacity at pH 6.8: slow buffers have higher pKa and lower buffer capacity, fast buffers higher buffer capacity and a pKa near the dissolution pH [rests on: R2; pKa in B1] | p.4 |
| C20 | claim, prior hypothesis, authors: "It is well known" | The dissolution rate of enteric polymers depends on the buffer capacity of the medium [rests on: cited: ref 19] | p.6 |

## 2023 Bapat — Does Media Choice Matter When Evaluating the Performance of Hydroxypropyl Methylcellulose Acetate Succinate-Based Amorphous Solid Dispersions? · Dissolution / A. Release mechanism and LoC

[2023-bapat-hpmcas-asd-media-choice-buffer-capacity-release](../../../cards/2023-bapat-hpmcas-asd-media-choice-buffer-capacity-release/paper.html) · Dissolution / A. Release mechanism and LoC · measured · as: buffer capacity

| id | kind | content | locator |
|---|---|---|---|
| R5 | record, measured | normalized release rate of neat HPMCAS by medium — neat HPMCAS compacts (P7), 100 rpm — sub-table below | Fig. 2, p.5717; text p.5718-5719 |
| R14 | record, measured | gel layer at the compact surface (confocal cross-section) — neat HPMCAS with prodan, 60 min in pH 6.8 phosphate (P9) — dry compact: grain boundaries between particles, no gel. 5 mM/ΔpH: no gel layer visible. 13 mM/ΔpH: gel 3 ± 1 µm (text); labelled widths 4.11, 3.54, 4.29 µm. 26 mM/ΔpH: labelled widths 6.37, 5.60 µm (no value in text). 51 mM/ΔpH: 19 ± 5 µm (text); labelled widths 13.98, 13.70, 24.03 µm. Gel seen as a lighter layer without grain boundaries; seen only from 13 mM/ΔpH upward; thickness rises with buffer capacity | Fig. 6, p.5721; text p.5720 |
| R15 | record, measured | gel layer apparent pH (mean ± SD) — gel removed from compacts after exposure in the IDR apparatus (P10) — sub-table below | p.5720; methods p.5717-5718 |
| A1 | scope item | buffer capacity of pH 6.8 phosphate — 3, 5, 13, 26, 51 mM/ΔpH (5, 10, 25, 50, 100 mM; P14.b-f) — 37 °C, 100 rpm, 0.5 cm² compact face, 100 mL — normalized release rate of HPMCAS and drug; gel thickness; gel apparent pH |  |
| C9 | claim, conclusion, authors: "readily apparent", "strong dependence"; plateau: "may be approaching" | HPMCAS dissolution rate depends strongly on buffer capacity in pH 6.8 phosphate, particularly at low buffer capacity; at higher buffer capacity it is less dependent and may approach a plateau [rests on: R5.a-e] | p.5718 |
| C50 | claim, conclusion, authors: asserted | Polymer release rate is a strong function of buffer capacity, buffer species, bulk pH, hydrodynamics and DL [rests on: R5, R11, R18] | p.5724 |

## 2024 Bapat — Interplay of Drug−Polymer Interactions and Release Performance for HPMCAS-Based Amorphous Solid Dispersions · Dissolution / A. Release mechanism and LoC

[2024-bapat-hpmcas-drug-polymer-complexation-release-performance](../../../cards/2024-bapat-hpmcas-drug-polymer-complexation-release-performance/paper.html) · Dissolution / A. Release mechanism and LoC · used · as: buffer capacity

| id | kind | content | locator |
|---|---|---|---|
| C13 | claim, mechanism, authors: asserted ("results from") | The lower release of neat HPMCAS in pH 9.0 glycine/NaOH buffer results from the low buffer capacity of that buffer (pKa 9.0) at the dissolving interface, whose pH is much lower than the bulk; the tablet formed no gel layer there, placing surface pH below 5.5 [rests on: R4.g, R20; cited: ref 46] | p.1470 |
| C44 | claim, generalisation, authors: "likely" | Drug chemistry, pKa and log P, the buffer capacity, pH and ionic strength of the medium (through gel or boundary layer pH) and DL are all likely determinants of release from HPMCAS ASDs, with implications for polymer choice [rests on: R2, R4, R6, R13, R15] | p.1475 |
| R6 | record, measured | normalized release rates in 50 and 100 mM pH 6.8 phosphate, mg·min⁻¹·cm⁻² (n = 3) — neat HPMCAS and LOR:HPMCAS 25:75 ASD, P7 — figure: neat HPMCAS ≈0.91 (50 mM), ≈1.00 (100 mM); ASD LOR ≈0.10 and HPMCAS ≈0.12 (50 mM), LOR ≈0.25 and HPMCAS ≈0.29 (100 mM) (read from Fig. 6); text: ASD release of both components improved by a factor of ∼2.9, neat HPMCAS by ∼1.2 | Fig. 6, p.1471; text p.1470 |

## 2025 Fagan — Impact of Permeation Enhancers on the Release of Insulin from Tablets in Biorelevant Media · Peptide permeability / Peptide permeability

[2025-fagan-permeation-enhancers-insulin-minitablet-biorelevant-media](../../../cards/2025-fagan-permeation-enhancers-insulin-minitablet-biorelevant-media/paper.html) · Peptide permeability / Peptide permeability · used · as: buffer capacity

| id | kind | content | locator |
|---|---|---|---|
| C8 | claim, conclusion, authors: asserted ("significant increase") | excess enhancer raises the pH of every medium, C10 to between 8.8 and 9.2 and SNAC to between 7.6 and 7.9, while excess insulin does not appear to change it [rests on: R5] | text p. 4002 |
| X1 | extractor note | source inconsistency — the Table 1 row is labelled "buffer capacity (Osm/L)", but osmoles per litre is a tonicity unit and the three values 270, 670 and 120 are the osmolality figures usually quoted for these media, not buffer capacities in mmol per litre per pH unit — P1, P4 — read the row as osmolality and take the buffer capacity as unreported |  |